1. Technical Field
The present invention relates to an electrical fuse, a semiconductor device, and a method of disconnecting an electrical fuse.
2. Related Art
There has been known techniques of preliminarily mounting fuses on semiconductor devices, and disconnecting or blowing the fuses in order to adjust resistivity of resistors used for the semiconductor devices, or in order to disconnect any defective elements and replace them with normal elements.
Known methods of disconnecting the fuses include those of irradiating laser to a portion of each fuse, and those of allowing current to flow therethrough.
Japanese Laid-Open Patent Publication No. 2007-266061 describes an electrical fuse (e-fuse) configured to have a silicide layer on a polysilicon layer, wherein a part of the circumferential portion in adjacent to the contact region is configured by a non-silicide region. Since metal atoms may move by electro-migration into the non-silicide region, so that it is described that the electrical fuse once disconnected by electro-migration may be prevented from causing back-flow.
Japanese Laid-Open Patent Publication No. 2007-73576 describes a fuse element allowing at least a portion of a metal material, which composes a metal silicide layer formed over a silicon layer, to move to one contact portion side after disconnection, and allowing the other contact portion to connect with the silicon layer.
According to the method described in Japanese Laid-Open Patent Publication No. 2007-266061, the silicide layer is disconnected only by a mild electro-migration, so that the method is none other than disconnecting the silicide layer, while remaining the contacts and the silicide layer in connection with each other. The method was therefore only to produce small changes in the resistivity between the states before and after the disconnection of fuse, and to make judgment only to a limited degree of accuracy. On the other hand, Japanese Laid-Open Patent Publication No. 2007-73576 describes a configuration allowing the contact to connect with the silicon layer after the disconnection. Since the contact in this configuration is connected with the silicide layer before the disconnection, and is connected with the silicon layer after the disconnection, so that the fuse may supposedly be increased in changes in the resistivity between the states before and after the disconnection. The method described in Japanese Laid-Open Patent Publication No. 2007-73576 is, however, still none other than allowing a metal material composing the silicide layer to cause only a narrow portion of disconnection by a mild electro-migration, so that disconnected portion may be anticipated to recover connection, due to migration of the silicide layer. Also this configuration has, therefore, been suffering from a problem of only a limited degree of accuracy in judgment.